1. Field of the Invention
The present invention relates to a document processing apparatus which can output document information.
2. Related Background Art
As an apparatus for outputting document information, an ink-jet recording apparatus is known. The ink-jet recording apparatus has many advantages, e.g., low noise during recording, capability of high-density recording, and the like, and has received a great deal of attention in recent years.
Although the ink-jet recording apparatus can use standard paper as a recording medium, it may pose a problem as to a fixing property depending on the kinds of standard paper used. More specifically, since the ink-jet recording apparatus employs an ink (liquid) as a recording agent, if a recording medium has a poor ink absorption property, the ink cannot be quickly soaked in the recording medium, and non-absorbed ink remains on the recording medium as a liquid.
When such a state occurs, a conveying member such as a roller is contaminated with the ink, and the ink contaminating the conveying member is transferred onto the surface of the next recording medium, thus considerably impairing recording quality. Furthermore, when an operator handles recorded recording media, not only his or her hand is stained, but also the ink is smeared by rubbing, thus degrading image quality.
When recorded recording media are stacked on, e.g., a tray, the same problem is posed since the recording media are rubbed on the tray.
As a method of preventing the problem and improving a fixing property of the ink to a recording medium, the recording medium is heated by a heater to accelerate evaporation of an aqueous component contained in an ink, so that the ink on the recording medium is quickly dried and solidified. In order to meet the demand for shortening a recording medium convey path length and preventing a conveying member from being contaminated, a fixing heater is arranged near a recording position of a recording head, e.g., on a platen, opposing the recording head, for regulating the recording medium to be flat.
A wordprocessor often performs a print operation which requires a long signal processing time, e.g., modified character or illustration printing, rotation printing, or the like. In this case, a sufficient time can be assured for fixing. Contrary to this, in a normal print mode, a time for fixing is often insufficient. When an ink is to be sufficiently fixed in the normal print mode, a specific portion of a paper sheet is excessively heated in the above-mentioned special print mode which requires a long time for signal processing, as described above, and the paper sheet is excessively dried and shrunk, so that troubles, e.g., offset of ruled lines, may occur. When both a pattern which requires a long processing time and a pattern which does not require a long processing time are present at the same time, a countermeasure for such situation is never considered.
In a document processing apparatus which comprises a conventional ink-jet recording apparatus, since various paper sheets having, e.g., different ink fixing properties are heated by a heater at the same temperature, when, e.g., a high-density pattern such as a graph, an image, or the like is printed in a high-temperature, high-humidity atmosphere, a fixing property is poor, and a non-fixed paper sheet may be fed after the print operation, thus contaminating paper sheets.
When an ink-jet recording apparatus is used as an output device of a computer, a work station, and the like, since these host apparatuses require only a short signal processing time for printing, it is demonstrated that a temperature of a contact surface between a recording medium and a fixing heater preferably falls within a range of 60.degree. C. to 80.degree. C. to perform satisfactory and quick fixing without curling a recording medium.
When the ink-jet recording apparatus is used as the output device of a wordprocessor, since a signal processing time required for printing normal characters (images whose patterns are prestored in a wordprocessor main body) can be very short, satisfactory fixing processing can be performed even if a temperature of a contact surface between the recording medium and the fixing heater falls within a range of 60.degree. C. to 80.degree. C. However, signal processing for printing specific images whose patterns are not prestored in the wordprocessor main body, e.g., modified characters, illustrations, rotation printing, and the like requires a long period of time.
In this case, a recording medium stands still on the fixing heater for a long period of time, and a portion, heated by the heater, of a recording medium which absorbs a moisture in a high-humidity atmosphere is dried and shrunk. As a result, ruled lines are offset, and a sheet surface is locally roughened or curled. In the worst case, the curled portion is brought into contact with an ink-jet head, so that the surface of the recording medium is contaminated with ink, or the head is damaged.